Hydraulic vibration damper



March 23, 1954 R LUGN 2,672,955

HYDRAULIC VIBRATION DAMPER Filed Nov. 28, 1951 3 Sheets-Sheet l March 23, 1954 R LUCLEN 2,672,955

HYDRAULIC VIBRATION DAMPR Filed Nov. 28, 1951 3 Sheets-Sheet 2 March 23, 1954 R. LUCIEN 2,672,955

HYDRAULIC VIBRATION DAMPER Filed Nov. 28, 1951 3 Sheets-Sheet 3 Patented Mar. 23, 1954 HYDRAULIC VIBRATION DAMPER Ren Lucien, Paris, France, assignor to Societe dlnventions Aeronautiques et Mecaniques S. I. A. M., Fribourg, Switzerland, a corporation of Switzerland Application November 28, v1951, Serial No. 258,716

Claims priority, application France August 17, 1951 (Cl. 18S-94) 1 Claim. l

The present invention relates to hydraulic vibration dampers or dash-pots of the type comprising an immersed double-acting piston, wherein a piston driven by the member subjectedy to the vibrations divides two chambers, one between each of its opposite faces and the corresponding end of the cylinder in which it moves, each of which alternately forms the working chamber, according to the direction of movement of the piston, and which with one another by passages formed through the piston, members being provided between the said chambers and the passages to control the circulation of the liquid between the two chambers for the purpose of providing the required damping effect.

The piston of the hydraulic damping device according to this invention is designed to meet, by means of the members provided therein, all the operational requirements arising out of the application of the damping arrangement in question to a particular type of vehicle and to damp appropriately the vibrations received for each of the two directions of movement of the piston.

In accordance with the invention, this result is obtained by the combined action of a sliding valve and a suitably calibrated spring co-operating therewith, the said valve consisting of a cylindrical body which is internally hollowed and mounted in a bore in the piston and which comprises over part of its side wall, longitudinal slots which, for some positions of the valve, constitute throttling means which cause loss of pressure in the liquid and through which the said liquid, compressed in one of the two chambers changes to the expanded condition in the opposite chamber, the said loss of pressure thus taking place in the immediate neighbourhood of the momentarily active face of the piston.

A constructional form of the hydraulic vibration damper according to the invention is illustrated by way of example in the accompanying drawings, in which:

Figure 1 is .an axial longitudinal sectional view of the damper;

Figure 2 is a View in section on the line A-A of Figure l;

Figure 3 is a sectional view on the line B-B of Figure 1 and,

Figure 4 is a fragmentary sectional view showing on a larger scale the details of the sliding valve and of the calibrated spring co-operating therewith.

In these drawings, the parts which are the same at the two ends of the piston are designated by the same reference numerals, the index a being added for the parts at one end.

The piston I driven by the arm 2 connected to the shaft 3 of which the vibrations are to be damped moves in the cylinder 4 closed at each end by fluid-tight covers 5 and 5a.

Mounted in each of the bores 6, 6a formed in the body of the piston l is a sliding valve 1, la, the said sliding valves being situated at the points at which the said bores lead into the chambers vi3 .and 3a respectively enclosed by each of the end-faces of the piston and of the corresponding end of the cylinder 4.

The said slide valve, the course of which is limited by the abutment ring 9, 9a, co-operates with a compression spring I0, Illa, lodged in the corresponding bore 6, Sa, and it has in one part of its side wall, slots II, I Ia. There is preferably formed in the end ofthe said sliding valve a calibrated oriice 22, y22a of very small sectional area with respect to the slots II, Ila.

Passages I2 and I2a respectively formed in the body of the piston afford communication between each of the chambers 8 and 8a respectively and the bore 6a, 6 corresponding to the opposite chamber. Each of the said passages leads into the bore through two ducts, one of which, I3, I3a, leads into a circular groove I5, I5a formed in the said bore, while the other I4, I 4a leads into the same bore a little to the rear of the former.

In addition, two passages I6, ISa opening into the central spaces Il, filled by the reserve liquid. lead to the chambers 8, 8a, there being provided at the outlets from the said passages into each of the said chambers a shut-off valve I8, I8a of the known lamellar type, the said valve being provided with a stroke-limiting device I9, Isa.

Assuming that the vibration to be damped has the effect of moving the piston in the direction of the arrow f, the liquid will be compressed in the chamber 8, the passages I2, I3a and I4a and the bore 6a, and will be expanded in the chamber 8a, the passages I 2a, I3 and I4 and the bore 6.

When the position I is stationary, or if its speed is very low, the slide valve 'l is held against its abutment 9 by the action of the spring I0. In this case, the two chambers 8 and 8a can communicate with one another only through the fixed orices of very small area I2, I2a in the slide valves and through the clearances resulting from the movements due to the manufacturing tolerances, because in this position the slots II are masked by the bore 6.

When the speed of the piston travelling in the direction f reaches a certain value, the slide Valve I moves under the action of the iiuid compressed in the chamber 8, thus compressing the opposing spring I0 (position illustrated in Figure 4). The-slots. `I I 'coeopenatingewitla'fthe 7annular; groove I5iidene aivariable fluid-th'rettlingfsec-N tion, the said section beingdetermined, in conjunction with the calibration and the deflection-f'. of the spring I0, as a function of.the,.conditions. to be fulfilled for the required damping effect.A '1.0'" It is to be noted that the saidithrottlingiandzthee pressure drop resulting therefronritakefplcevin the immediate neighbourhood ofthatfface =of-th`ef= piston which encloses in this phase of operation the chamber in which the liquidss'isompressedn At this instant, the liquid under pressurefin the l chamber 8 cannot pass freely into- =thefopp0sitef chamber 8a because it is stopped bythe valve f 1a, which is held against its abutment 9apwithf its ports Ila covered byffthe bore 6a, that is ,tov 20 say, out of communication with the groove [5a.

O'Wingrto the transfer" of ."the liquidfrom' one i. working chamber' into5the 'othentheshut-offf valves-18;* 18d on'lyoperate ac':identallytwh'enfalA contraction of the "liquid," duerto. atemperaturefl 25 reduction; sets up a*pre'ssuredi"erencef'between'i 14 the chambers in' 'Whichzth'e .'lilud'is. inrthe uncompressed state (that tto say:, ,the :chamber 8a inthe-ccase-of fthe-phase of;operationdegy scribed) and; the =reserve :containedwin' the cen-V p30 trarchambenl'll" l The Yliquid employed cin the damping arrangef` ment hereinbefore described.; is preferably. ,a binary. or ternary 1 quid;consstingcr. example, ojfa-mixture of"1inseed .,oi'lgjyalcoholgandcyclor. 35 f hexanol",` havingat leastoneelement; the *volar tility I`of which actsras '-afi stabiliser frxtha `vSrf cosity of the mixture-,r despitegtnetemperature increase resultingfromithe operation.

Inra hhydraulic dash=pnt-ofthetypeincluding 4 a piston, immersed in a huid-tight cylinder lled With fluid, wherein the piston defines in the cylf inder two chambers each enclosed between one face of the piston and the correspondingend of 5 thecylinder, anddfurth'ergzinclding@communicae ticnfducts-"between the twoch'ambers and slide valves forvarying the ow area for the fluid as the piston is reciprocated in the cylinder; the

piston comprising, at each face of the piston, a bore in thebody of the said piston opening on 'totheacorresponding face, an externally cy 'lndrical*hollWaslide-valve in each vsaid bore having'anopngon the side of the corresponding face of the'piston, a bottom Wall, and lateral r"slotssterminatingeatsaid opening, said botto-m Wall having 1a bleed hole'therein of very small Acmss-eseetibn-relatively to said slots, an abutment-for the said valve in the neighborhood of theffsaidface of 'the piston, a spring of suitable calibration disposed between the said Valve and the, closedL-endMofmthebore;,.a groove .formed-in the .bo1:e...in ',aepositi'orn to v lb'e closed by ,the slide valreswhenaat, resina yrst. communication. .duct int, th'e., bodiny of/lthe pistonxtending from the. Y SaidgIfOOVeto the .other 'sideliof Lthe piston-,and..a .v secpndcommunication ductsinthebody of theA pistoni intermediate .,.the...,position-unrest of the. slidevalre and,..the vc1sedend Ioiith'e `,bore and,.. extendihg.,frlom. the, lsaidL-bore to the t said,rst

duch, y v RENLUQIEN. Referneseciteafin'fthevnrefori this patent yrommeltrPATErrrs^,l Number Country Date@` J5E;225: Frame-e Jeans- 9, v195o 959299 i; France -Man 21,1950 Greatfgfritain Aug-9;- 1950 

